In this Jan. 31, 1985 photo, “Saturday Night Live” actor Billy Crystal, in character as “Fernando,” center, is flanked by host Alex Karras and musical guest Tina Turner during a rehearsal in New York.

Alex Karras, a fierce and relentless All-Pro lineman for the Detroit Lions whose irrepressible character placed him frequently at odds with football’s authorities but led to a second career as an actor on television and in the movies, died Wednesday at his home in Los Angeles. He was 77.

Karras had kidney disease, heart disease and stomach cancer, his family said in a statement announcing his death, as well as dementia. He was among the more than 3,500 former players who are suing the NFL in relation to the long-term damage caused by concussions and repeated hits to the head.

To those under 50, Karras may be best known as an actor. He made his film debut in 1968, playing himself in “Paper Lion,” an adaptation of George Plimpton’s book about his experience as an amateur playing quarterback for the Lions, which starred Alan Alda as Plimpton. His rendering of his own roguish personality led to several appearances on “The Tonight Show With Johnny Carson,” and in the 1970s he played numerous guest roles on series television, on shows like “McMillan and Wife,” “Love, American Style,” “M(AST)A(AST)S(AST)H” and “The Odd Couple,” in which he played a comically threatening man-mountain, the jealous husband of a woman who has become friendly with Felix (Tony Randall). Perhaps most memorably, he played Mongo, a hulking subliterate outlaw who delivers a knockout punch to a horse, in the Mel Brooks western spoof “Blazing Saddles.”

In 1975 he played George Zaharias, the husband of the champion track star and golfer Babe Didrickson Zaharias, in the television movie “Babe.” The title role was played by Susan Clark, who became his wife, and from 1983 to 1989, they starred together in the gentle sitcom “Webster,” about a retired football player who takes in a black boy (Emmanuel Lewis), the orphaned young son of a former teammate.

But Karras first earned fame as a ferocious tackle for the Lions, anchoring the defensive line for 12 seasons over 13 years, 1958-70. It was an era when the NFL was rife with talent at the position — Karras’ contemporaries included the Hall of Famers Bob Lilly and Merlin Olsen — but he was an especially versatile pass rusher, known around the league for his combination of strength, speed and caginess. His furious approach — Plimpton described it as a “savage, bustling style of attack” — earned him the nickname the Mad Duck.

“Most defensive tackles have one move, they bull head-on,” Doug Van Horn, a New York Giants offensive lineman who had to block Karras, said in 1969. “Not Alex. There is no other tackle like him. He has inside and outside moves, a bull move where he puts his head down and runs over you, or he’ll just stutter-step you like a ballet dancer.”

Karras was named to four Pro Bowls, and he was a member of the NFL’s All-Decade team of the 1960s. He was never elected to the Hall of Fame, however, an oversight that has sometimes been attributed to the fact that the Lions fielded mostly undistinguished teams during his tenure; in Karras’ only playoff game, the Lions lost to the Dallas Cowboys by the unlikely score of 5-0 in 1970.

But another theory is that his unwillingness to be an obedient NFL citizen — especially his antagonism toward the longtime NFL commissioner Pete Rozelle — resulted in an unofficial blackballing. Witty, brash and probably smarter than your average bear (or Lion or Packer of Giant, for that matter), Karras was, throughout his career, a thorn in the side of league authorities, speaking out against team owners in general and the Lions’ management in particular. He deplored the way players were treated like chattel on the one hand, deployed as seen fit, and children on the other, held to restrictive behavioral standards, scolded and disciplined.

His reputation as a league outlaw was cemented in 1963 when Rozelle suspended him indefinitely, along with Paul Hornung, the star running back of the Green Bay Packers, for betting on NFL games, and both players missed the entire season. Hornung was immediately contrite, but Karras was steamed, asserting that his half-dozen or so $50 and $100 wagers — neither man was accused of betting against his own team, providing inside information to gamblers or giving less than his best on the field — was a threat to the integrity of the game.

Later that year Karras reportedly sold his ownership share in the Lindell A.C., a Detroit bar that was frequented by athletes and, according to the Detroit police, “known hoodlums,” to convince Rozelle that he was repentant — he denied this later — and Rozelle reinstated both men after 11 months, in time for them to play in 1964. Shortly after Karras returned, an official asked him to call the pregame coin toss and Karras, with cheeky disdain, refused.

“I’m sorry, sir,” he explained, “but I’m not permitted to gamble.”

Alexander George Karras was born on July 15, 1935, in Gary, Ind., where his father, George, a Greek immigrant, was a doctor, and his mother, the former Emmeline Wilson, was a nurse. An all-state football player in high school, he attended the University of Iowa, where in 1957 he won the Outland Trophy as the outstanding interior lineman in college football. In 1958, he was drafted in the first round by the Lions.

Karras’ other film credits included roles in the raunchy comedy “Porky’s,” the suspense thriller “Against All Odds” and the gender confusion comedy “Victor/Victoria.” He spent three seasons in the broadcast booth, working with Howard Cosell and Frank Gifford on ABC’s “Monday Night Football,” and later wrote a novel, “Tuesday Night Football,” sending up his experience. He also wrote on autobiography, “Even Big Guys Cry.”

In addition to his wife, he is survived by their daughter, Katherine Karras; a sister, Nan Reisen; three brothers, Louis, Paul and Ted; several children from a previous marriage, Alex Jr., Peter, Carolyn Karras, George and Renald; and five grandchildren.

Karras named one of his sons after George Plimpton, and for years he told journalists he named another after Rozelle, as a way of remembering the humbling experience of his suspension. But he put an end to that charade in an interview with Sport magazine in 1970, in which he said that though he was wrong to gamble on games the punishment was overly harsh, and that Rozelle had used him to establish his reputation for toughness. His son Peter, he said, was named after his father-in-law.

“And I said, `Yeah, I named him after Rozelle,”’ he told the magazine, “which is a lie ‘cause I wouldn’t name anyone after that buzzard.”